// Generate four random hex digits.
function S4() {
  return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
}

// Generate a pseudo-GUID by concatenating random hexadecimal.
function guid() {
  return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());
}

function uuid() {
  return uuid(0,16)
}
 //指定长度和基数
function uuid(len, radix) {
  var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');
  if(!len){
    len = 32;//默认32个
  }
  if(!radix){
     radix = chars.length;
  }
  var uuid = [], i;
  radix = radix || chars.length;

  if (len) {
    // Compact form
    for (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random() * radix];
  } else {
    // rfc4122, version 4 form
    var r;

    // rfc4122 requires these characters
    uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
    uuid[14] = '4';

    // Fill in random data.  At i==19 set the high bits of clock sequence as
    // per rfc4122, sec. 4.1.5
    for (i = 0; i < 36; i++) {
      if (!uuid[i]) {
        r = 0 | Math.random() * 16;
        uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
      }
    }
  }

  return uuid.join('');
}

function uuidv4() {
  return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
      (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
  )
}
function generateUUID() { // Public Domain/MIT
  var d = new Date().getTime();
  if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
    d += performance.now(); //use high-precision timer if available
  }
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
    var r = (d + Math.random() * 16) % 16 | 0;
    d = Math.floor(d / 16);
    return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
  });
}

module.exports = {
  uuid,
  guid
}